JP2000114638A - Metallic vapor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metallic vapor laser device which can obtain a laser output having a low cost and being stable. SOLUTION: A metallic vapor laser device 1 is provided with a metallic vapor source 5 which internally generates metallic vapor, which generates the metallic vapor by heating an electric-discharge tube 2 in which buffer gas for discharging is filled, by discharge heating and which generates laser by exciting the metallic vapor, and has a gas flow volume controlling device 16 which controls and infuses the flow volume of the buffer gas for discharge into the inside of the electric-discharge tube 2, two system gas supplying tubes of a pure neon gas supplying tube 21 junctioned with the gas flow volume controlling device and a mixed gas supplying tube 22, a switching controlling device 25 which drives switching valves 23 and 24 for the two system gas supplying and a gas pressure controlling device 30 which controls a pressure of the buffer gas for discharge in the electric-discharge tube to be constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a metal vapor laser apparatus, and more particularly, to control of a buffer gas filled in a discharge tube.

[0002]

2. Description of the Related Art A metal vapor laser device is widely used as a large-sized laser device capable of continuous laser oscillation with a large output, for example, used for a metal working machine.

The above-mentioned large-sized, high-output metal vapor laser device includes a metal discharge source inside, a cylindrical discharge tube main body, and a pair of anode and cathode disposed at both ends of the discharge tube main body. , Outside each of the anode and cathode,
It has a well-known laser oscillation structure such as a pair of Brewster tubes, a total reflection mirror and an output mirror disposed further outside each Brewster tube. Also,
The discharge tube main body is insulated by a heat insulating material and a cylindrical body arranged so as to surround the outer peripheral surface.

One of the Brewster tubes is supplied with neon (Ne) gas as a discharge buffer gas. In addition,
As the discharge buffer gas, until the metal vapor is generated from the metal vapor source and laser oscillation starts,
Although only neon gas is used, when metal vapor is generated, the discharge resistance of the discharge buffer gas in the discharge tube main body decreases and the laser output fluctuates, so that 0.5 to 2 hydrogen is added to neon gas. % Mixed gas is used. For this reason, the Brewster tube that supplies neon gas to the discharge tube main body is formed so as to be able to supply both neon gas or a mixed gas obtained by mixing hydrogen with neon gas.

[0005] An exhaust pipe, a flow control valve, and a vacuum pump used for setting the concentration of the discharge buffer gas in the discharge tube main body to a predetermined concentration are connected to the other one of the Brewster tubes.

In such a metal vapor laser device, a discharge tube body is filled with neon gas and a high voltage is applied between an anode and a cathode to form discharge plasma, and the discharge tube body is heated. When the discharge tube main body is heated, vaporized metal particles, that is, metal vapor serving as a laser medium are generated from the metal evaporation source in the discharge tube main body. The metal vapor is excited by free electrons in the discharge plasma in the discharge tube body, and a laser beam is output when the excited metal vapor transitions to a low energy level.

As described above, when laser light is oscillated, the discharge resistance fluctuates due to metal vapor diffused in the discharge tube body, and as a result, the output of the oscillated laser light fluctuates. Therefore, it is necessary to keep the hydrogen concentration in the discharge buffer gas constant at the time when the laser light is oscillated. Since the output of the laser beam is also affected by the hydrogen concentration in the discharge buffer gas, at the time when the laser beam is oscillated, the discharge buffer gas is converted from neon gas (pure neon gas) to a predetermined ratio in advance. A method of switching to a mixed gas mixed with hydrogen is used.

[0008]

However, when switching the discharge buffer gas from a neon gas to a mixed gas, it is necessary to quickly detect the point at which laser oscillation is started and switch at an appropriate timing. in this case,
If the switching timing is slightly earlier than the start of laser oscillation, there is a problem that the laser output does not reach the rated value. On the other hand, if the switching timing is delayed more than necessary from the start of laser oscillation, there is a problem that the time required for the laser output to converge to an appropriate value increases.

When a large number of metal vapor laser devices are used, such as a metal working machine, the discharge buffer gas in the discharge tube body of all the metal vapor laser devices must be switched at the same time. There's a problem. In this case, if the switching time to the mixed gas is different for each laser device, the laser output obtained from each laser device varies, causing a problem that a stable laser output cannot be obtained as a laser system.

An object of the present invention is to provide a metal vapor laser device capable of obtaining a stable laser output at low cost.

[0011]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned problems, and has a metal vapor source for generating metal vapor therein, and discharges a discharge tube filled with a buffer gas for discharge. In a metal vapor laser apparatus which generates a metal vapor by heating and excites the metal vapor to generate a laser beam, the discharge buffer gas may be a pure neon gas or a mixed gas obtained by mixing a hydrogen gas with a neon gas. It is an object of the present invention to provide a metal vapor laser device characterized in that a mechanism for automatically switching the supply of each buffer gas is provided using a type.

Further, according to the present invention, a metal vapor source for generating metal vapor is provided therein, and a discharge tube filled with a discharge buffer gas is heated by discharge heating to generate metal vapor. A metal flow laser device that excites a laser beam to generate laser light, a gas flow control device that controls and injects a flow rate of the discharge buffer gas into the discharge tube, and a pure neon gas supply connected to the gas flow control device. A gas supply pipe of two systems of a pipe, a mixed gas supply pipe of neon gas and hydrogen, a switching control device for operating a valve for switching the gas supply of the two systems, and exhausting a discharge buffer gas in the discharge tube; A gas pressure control device for controlling the pressure of the discharge buffer gas in the discharge tube to be constant. Than it is.

Further, the present invention is characterized in that the discharge buffer gas is switched from a neon gas to a mixed gas based on any one of an elapsed time from the start of the discharge, generation of a laser output, and a decrease in a discharge resistance. A metal vapor laser device is provided.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic view of a metal vapor laser device capable of continuous laser oscillation with high output.

As shown in FIG. 1, the metal vapor laser device 1 has a discharge tube main body (ceramic tube) 2 made of ceramic or the like. An anode 3 and a cathode 4 are connected to both ends of the ceramic tube 2 so as to face each other. A plurality of metal vapor sources 5 are arranged inside the ceramic tube 2. In the laser device shown in FIG. 1, copper is preferably used as a metal evaporation source.

The ceramic tube 2 is insulated by a heat insulating material 6. The periphery of the heat insulating material 6 is covered with a metal body 7. The body 7 is insulated by the insulating cylinder 8.

A pair of Brewster tubes 9a and 9b are connected outside the anode 3 and the cathode 4 at both ends of the ceramic tube 2. In addition, each Brewster tube 9a, 9
In b, windows 10a and 10b for transmitting the laser light oscillated inside the ceramic tube 2 are arranged. A total reflection mirror 11 and an output mirror 12 are arranged outside the windows 10a and 10b.

One Brewster tube 9 connected to the cathode 4
a denotes a gas supply pipe 13 connected to a gas supply system (described later) for supplying a buffer gas for discharge, and a blaster pipe 9b connected to the anode 3 connects to an exhaust pipe 14 for exhausting the buffer gas for discharge. , Are connected respectively.

A gate valve 15 for supplying / stopping a buffer gas from a gas supply system to the ceramic tube 2 (Brewster tube 9a) is connected to the gas supply tube 13.

The gate valve 15 is connected to a flow measurement controller 16 for measuring the flow rate of the discharge buffer gas and controlling the opening of the gate valve 15, that is, the flow rate of the discharge buffer gas.

The flow measurement control device 16 includes a gas supply system 2
0 is connected.

The gas supply system 20 has two gas supply pipes including a neon gas supply system 21 for supplying neon gas and a mixed gas supply system 22 for supplying a mixed gas in which neon gas and hydrogen are mixed at a predetermined ratio. I have.

The supply / stop of the neon gas from the neon gas supply system 21 and the supply / stop of the mixed gas from the mixed gas supply system 22 are provided between each of the gas supply systems 21 and 22 and the flow rate measurement control device 16. First and second control valves 23 and 24 that can be remotely operated by an external control signal are connected. In addition, each control valve 21,22
Are electrically connected to the main controller 25.

The main controller 25 is also electrically connected to a high-speed high-voltage discharge circuit (pulse power supply) 26.

On the other hand, the exhaust pipe 14 is connected to a vacuum exhaust system 30 for keeping the pressure of the discharge buffer gas in the discharge tube (ceramic tube) 2 constant.

The evacuation system 30 includes an evacuation pump system 31
And a flow control valve 32 disposed between the vacuum pumping system 31 and the exhaust pipe 11 to set the pressure of the discharge buffer gas in the ceramic pipe 2 to be constant.

Next, the laser beam oscillation and the control of the discharge buffer gas in the above-described metal vapor laser apparatus will be described in detail.

First, the exhaust pump system 31 is operated to evacuate the inside of the discharge tube 2. After the evacuation, the valves 15, 23 and 24 are closed so that the gas flow from the gas supply tube 13 becomes zero. I do.

Next, the first control valve 23 is opened, and the opening of the first control valve 23 is adjusted by the flow rate measurement control device 16 so that the neon gas (discharge buffer gas) is supplied at a predetermined flow rate (approximately (1 liter / hour). At this time, the pressure of the buffer gas in the discharge tube 2 that rises due to the injection of the discharge buffer gas (neon gas) is adjusted to a preset pressure by the vacuum exhaust system 30.

Subsequently, the pulse power supply 26 is operated to generate plasma in the discharge tube 2, and the plasma causes the metal vapor source 5 to rise to a temperature at which metal vapor can be generated. In the case where copper is used as the metal evaporation source 5 in the laser apparatus shown in FIG. 1 as described above, the temperature required for laser oscillation is approximately 1500 ° C. When the temperature is raised, the body 7 connected to the electrode support flanges 3a and 4a for holding the anode 3 and the cathode 4 is used.
And the pulse power supply 26 connected to the connection point 7a installed on the body 7, has a rise time of about 10-7 seconds or less, a repetition frequency of several kHz to several tens kHz, and a voltage of tens of kV to A pulse high voltage of several tens of kV is used.

By maintaining this state, metal (copper) vapor (copper particles) is uniformly distributed in the ceramic tube (discharge tube) 2.

When free electrons in the plasma collide with the metal (copper) vapor, the copper particles are excited, and the inside of the ceramic tube 2 has a population inversion state. In this state, when the excited metal vapor (copper particles) transitions to a low energy level, laser beams having wavelengths of 511 nm and 578 nm are generated.

In this way, the laser light generated in the ceramic tube 2 passes through the windows 13a and 13b, and its amplitude is amplified while being reflected by the total reflection mirror 14 and the output mirror 15 constituting the laser resonator. Then, at the time when the signal is amplified to a predetermined level, the light is emitted from the output mirror 15 as laser light.

By the way, in the above-mentioned laser apparatus, the electric power is reduced due to the influence of metal (copper) vapor and the injection of discharge energy is reduced at the same time as the start of discharge in the discharge tube 2, so that the laser output is reduced. It is known to decrease.

Therefore, as described above, in the metal vapor laser apparatus, it is necessary to switch the discharge buffer gas from a pure neon gas to a mixed discharge buffer gas of neon and hydrogen when the laser beam starts to oscillate. There is.

This switching operation is performed, for example, by using metal (copper).
Since it is well known that the electric resistance decreases due to the generation of steam, the relationship between the time during which the discharge tube 2 is heated by the plasma and the decrease in the electric resistance is measured in advance, and after the time obtained by the measurement, the main control is performed. It is executed under the control of the device 25. In a copper vapor laser device, it is known that the laser output becomes maximum when the temperature of copper is approximately 1500 ° C. In this case, an exponential relationship as shown in FIG. 2 is established between the density of copper vapor and the temperature of copper. When the temperature of copper is 1500 ° C. and sufficient copper vapor is generated, the electric resistance in the discharge tube 2 becomes
It generally drops below 5 ohms. On the other hand, when the copper vapor is not sufficiently generated, the electric resistance becomes several hundred Ω or more. In this case, the main control device 25 closes the first control valve 23 to stop the supply of the pure neon gas, and simultaneously opens the second control valve 24, and the flow rate measurement control device 16 controls the second control valve 24. The opening degree is adjusted, and a mixed gas (discharge buffer gas) in which neon gas and hydrogen are previously mixed at a predetermined ratio is injected into the discharge tube 2 at a predetermined flow rate. The pressure of the mixed gas is controlled by the evacuation system 30.
The pressure is adjusted to a preset pressure.

By performing the switching of the discharge buffer gas at the same time as the decrease in the electric resistance based on the detection result of the electric resistance, the fluctuation of the laser output can be suppressed. In this case, by previously measuring the relationship between the time during which the discharge tube 2 is heated by the plasma and the decrease in the electrical resistance, it is possible to simply switch the discharge buffer gas based on the temperature rising time. Become.

The electric resistance at the time of discharging can also be obtained from the measured value of the applied voltage and the measured value of the discharge current. In this case, for example, when the resistance drops below a predetermined resistance value (about 5 ohms), the main controller 25 may switch the discharge buffer gas.

Further, when the applied voltage is constant, the point in time when the discharge current exceeds a predetermined value (about 2600 A) can be regarded as the electric resistance has dropped below the predetermined value.

Further, the intensity of the microlaser oscillation generated by the generation of the copper (metal) vapor may be measured, and the discharge buffer gas may be switched when the laser output exceeds 1 W, for example.

Even when the three electrical resistances are obtained by any of the above-described methods, there is no need to add a new measuring device to the metal vapor laser device, so that the cost of the device does not increase.

As described above, according to the embodiment of the present invention, the discharge buffer gas can be switched from neon gas to a mixed gas of neon gas and hydrogen almost at the same time when the laser beam is generated. Thereby, the laser output is converged to a predetermined value in a short time and is stabilized. Further, when a large number of laser devices are used at the same time, the switching of the buffer gas in each laser device can be switched at substantially the same time, so that a stable laser output can be obtained.

[0044]

As described above, according to the present invention,
The buffer gas can be switched from neon gas to a mixed gas of neon gas and hydrogen in a short time after the laser output of the laser device is generated. Further, when a large number of laser devices are used at the same time, the switching of the buffer gas in each laser device can be switched at substantially the same time, so that a stable laser output can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a copper temperature and a copper vapor density in a discharge tube of the copper vapor laser device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Metal vapor laser apparatus, 2 ... Ceramic tube (discharge tube main body), 3 ... Anode, 4 ... Cathode, 5 ... Metal vapor source, 6 ... Heat insulation material, 7 ··· Body, 8 ··· insulating tube, 9a ··· Brewster tube, 9b ··· Brewster tube, 10a ··· window, 10b ··· window, 11 ··· total reflection mirror, 12 ··· output Mirror 13 gas supply pipe 14 exhaust pipe 15 gate valve 16 flow measurement control device 20 gas supply system 21 neon gas supply system 22 ... mixed gas supply system 23 ... first control valve 24 ... second control valve 25 ... main controller 26 ... high-speed high-voltage discharge circuit (pulse power supply) 30 evacuating system 31 evacuating pump system 32 flow control valve

Claims (5)

[Claims] 1. A metal vapor source for generating a metal vapor is installed therein. A discharge tube filled with a discharge buffer gas is heated by discharge heating to generate a metal vapor, and the metal vapor is excited. In a metal vapor laser device that generates laser light, a mechanism for automatically switching supply of each buffer gas using two types of pure neon gas or a mixed gas obtained by mixing hydrogen gas with neon gas as the discharge buffer gas is used. A metal vapor laser device characterized by being provided. 2. The metal vapor laser device according to claim 1, wherein the pure neon gas and the mixed gas are switched based on the time from the start of discharge. 3. The metal vapor laser device according to claim 1, wherein said pure neon gas and said mixed gas are switched by detecting generation of a laser output. 4. The metal vapor laser device according to claim 1, wherein the pure neon gas and the mixed gas are switched when a discharge resistance during discharge becomes lower than a predetermined resistance value. 5. A metal vapor source for generating metal vapor is installed therein, and a discharge tube filled with a discharge buffer gas is heated by discharge heating to generate metal vapor, and the metal vapor is excited. In a metal vapor laser device that generates laser light, a gas flow control device that controls and injects a flow rate of the discharge buffer gas into the discharge tube, a pure neon gas supply pipe and a neon gas connected to the gas flow control device Two gas supply pipes including a hydrogen mixed gas supply pipe, a switching control device that operates a valve for switching between the two gas supply systems, and a discharge buffer gas in the discharge tube is exhausted. A gas pressure controller for controlling the pressure of the discharge buffer gas to be constant.